America goes on a diet.

• Author: Majerol, Veronica
• Position: NATIONAL

Alter decades of overeating, Americans are finally consuming fewer calories. But there's still lots of room for improvement.

Julia Tofan used to be a regular soda drinker. But a couple of years ago, the 16-year-old from Hebron, Connecticut, started paying more attention to all the news about how unhealthy sugary drinks are. She began limiting herself to having soda only at parties and other social gatherings. Then last year, she cut it out altogether.

"I decided it wasn't healthy calorie-wise," she says. "And I didn't like the idea of artificial ingredients and preservatives, so I stopped."

Julia isn't alone. For the first time in 40 years, Americans are cutting back on calories. The reductions, which have taken place over the past decade, have been most dramatic among young children and households with children, and the biggest cuts across the board have been in soda consumption, according to a recent study published in The American Journal of Clinical Nutrition. At the same time, obesity rates appear to have stopped rising for adults and school-age children, suggesting the calorie cuts are starting to make a difference.

"This was like a freight train going downhill without brakes," says Kelly Brownell, dean of the Sanford School of Public Policy at Duke University in North Carolina. "Anything slowing it down is good."

How We Got Fat

American waistlines started expanding in the 1980s as a result of several factors. Among the main factors, according to Marion Nestle, a food studies professor at New York University, was the rise of large-scale industrial farming, encouraged by new government policies intended to spur agricultural production. With the help of fertilizers, pesticides, and high-tech machines, these farms could pump out crops like corn and soy in amounts never before seen. All that supply drove food prices down, which had ripple effects on the American diet.

"People ate out more, there was an enormous growth in the number of fast-food places, portions got larger, and food became ubiquitous," says Nestle. "Suddenly every single store, no matter what they were selling, had candy bars or some kind of food available."

At the same time, Nestle says, efforts to limit junk-food advertising aimed at children and teens was shot down by Congress, so marketers felt emboldened to advertise more than ever.

By the 1990s--around the time McDonald's introduced its 42-ounce "supersize" soda and other fast-food outlets followed suit--America was...